Aqueous-soluble Hyperbanched Polyesters: Snthesis And Photoresists For Microoptics

This work is about the synthesis of hyperbranched polyesters via a new approach, the modification of chain-end terminal groups to introduce photocuring functionality, and the application as resin of photoresist for fabrication of micro-optical elements. The polyesters synthesized from the reaction of trmellitic anhydride and epichlorohydrin in DMF at 110癈 were functionalized with GMA to introduce acrylox groups at chain-ends. Model reaction revealed that the reaction of -COOH with epoxyl and anhydride with -OH groups were at the same rate. Their alternated reactions lead to forming of polyesters. Direct reaction of桟OOH with -OH, -OH with epoxyl and -COOH with chloromethyl were neglectable under the polymerization condition. The two -COOH groups on trimellitic anhydride after esterization with alcohol showed about the same activity toward the epoxyl. Oligomeric hyperbranched polyester with narrow molecular weigh distribution (DPI - 1.3) synthesized and well characterized by FT-IR, 'H-NMR, 13C-NMR, UV, GPC, DSC and TGA. Photocuring behaviors of the resin and resists based on it were studied. Sensitivity and contract of the resists measured by gel content method were tunable by the PI. cross-ling monomer and developing solution. High sensitivity and low contract (E0 gel and Y were 5.5mJ/cm2 and 8.31, respectively) were realized in a case. Resolution reached about 1 u m by contact exposure. Optical micrography showed that etching was clear and clean. Photoresists for micro optical elements were studied using the hyperbranched polymer. The resists exhibited unique behaviors in the linear responses of etching depth to exposing energy. This linear behavior is not found on other resists as we could found. It provided the controlling of surface profile for the fabrication. Microlens array was prepared using the resists with a moving-mask. The micro lens (200 x 200 V- m) was well matched with the designed shape, and the height was as high as over 56 u m, comparing with < 30 u mby commercial resists.